Integrated digital active phased array antenna and wingtip collision avoidance system

ABSTRACT

A radar system to detect and track objects in three dimensions. The radar system including antennae, transmit, receive and processing electronics is all in a small, lightweight, low-cost, highly integrated package. The radar system uses a wide azimuth, narrow elevation radar pattern to detect objects and a Wi-Fi radio to communicate to one or more receiving and display units. One application may include mounting the radar system in an existing radome on an aircraft to detect and avoid objects during ground operations. Objects may include other moving aircraft, ground vehicles, buildings or other structures that may be in the area. The system may transmit information to both pilot and ground crew.

This application claims the benefit of U.S. Provisional Application No.62/343,704, filed May 31, 2016, the entire content of which is herebyincorporated by reference.

TECHNICAL FIELD

The disclosure relates to collision avoidance systems and antennas foruse in collision avoidance systems.

BACKGROUND

Detecting and tracking nearby objects may be useful, particularly foraircraft during ground operations. Ground collisions between aircraftand other objects, such as other aircraft, ground vehicles andstructures such as buildings can cause expensive damage and may bedangerous. Aircraft taxiing for takeoff often have full fuel tanks,which may rupture during a collision leading to possible fire orexplosion. Some solutions have radar or other sensors placed at the onthe aircraft to detect potential obstacles and present information tothe pilot on a human-machine interface (e.g., head-up, head-down, orhead-mounted display). Having such information available may improvepilot awareness of obstacles and help evaluate if a particular obstacleis a threat. Some systems provide information about only the laterallocation of obstacles relative to an aircraft, which may not explicitlyaddress whether the height of the wing, wingtips, or engine nacelle willclear the obstacles. Three-dimensional information about potentialdangers may be more valuable than just lateral information. Some systemsmay be expensive or impossible to install because the system may requireexpensive rework to run power and signal cables between the sensors andthe display unit in the cockpit.

Other systems may include radar sensors mounted on the wingtips thattake advantage of existing lighting to ‘see’ through the protectiveglass that covers the lighting. Non-standard glass material andthickness may cause transmission and accuracy issues for these radarsensors. Also, any modifications to the wings may interfere with deicingsystems, moveable wing structures such as Fowler flaps or require cablesrunning near or through fuel tanks, which may be in the wings of manycommercial aircraft. Therefore, modifications to the wings may havedisadvantages in that modifications may impact safety and aircraftcertification. Any collision avoidance system mounted in an aircraftwing may likely be part of the aircraft original design.

SUMMARY

In general, this disclosure is directed to various techniques related tocollision avoidance systems and antennas for use in such collisionavoidance systems. A collision avoidance system in accordance with thetechniques of this disclosure may use radar to detect unwanted objectsin a coverage area, and in response to detecting an unwanted object inthe coverage area, send a notification to an operator.

In one example, this disclosure is directed to an obstacle detectionsystem comprising: a slotted waveguide radar transmit antenna, a slottedwaveguide radar receive antenna, radar transmitter electronics in signalcommunication with the slotted waveguide radar transmit antenna, whereinthe radar transmitter electronics, in conjunction with the slottedwaveguide radar transmit antenna, are configured to output monopulseradar signals. The obstacle detection system may also include radarreceiver electronics in signal communication with the slotted waveguideradar receive antenna, wherein the radar receiver electronics includedigital beam forming circuitry configured to receive from the radarreceive antenna radar reflections corresponding to the outputtedmonopulse radar signals. Additionally, the obstacle detection system mayinclude one or more processors configured to generate a notification oftarget detection information based on the radar reflections and whereinthe slotted waveguide radar transmit antenna, the slotted waveguideradar receive antenna, the radar transmitter electronics, radar receiverelectronics and the one or more processors comprise a single, integratedpackage. The obstacle detection system may, for example, be implementedon or into an aircraft, an automobile, a sea vessel, or any othersimilar type of vehicle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a conceptual diagram illustrating an example coverage area ofa collision avoidance system mounted on an aircraft.

FIG. 1B is a conceptual diagram illustrating a more detailed view of anexample position of a collision avoidance system mounted in a verticalstabilizer of an aircraft.

FIG. 2A is a conceptual and assembly diagram illustrating an explodedview of an example integrated radar system, which may be a component ofa collision avoidance system in accordance with one or more techniquesof this disclosure.

FIG. 2B is a conceptual diagram illustrating the transmission, receive,and communication antennae of an example integrated radar system, whichmay be a component of a collision avoidance system in accordance withone or more techniques of this disclosure.

FIG. 3A is a three-dimensional view illustrating an example substrateintegrated waveguide (SIW) element in accordance with one or moretechniques of this disclosure.

FIG. 3B illustrates a section of an example slot waveguide antenna arraysystem with a separate mixer for each channel.

FIG. 3C illustrates a section of an example slot waveguide antenna arraysystem with a four-channel mixer and single SIW portion connecting themixer to a power divider and a local oscillator (LO).

FIG. 3D is a two-dimensional view of an example SIW element illustratingdimensions and spacing in accordance with one or more techniques of thisdisclosure.

FIG. 3E is a three-dimensional view of an example SIW power divider inaccordance with one or more techniques of this disclosure.

FIG. 3F is a two-dimensional view of an example slot waveguide antennaarray system illustrating dimensions for coupling slot and microstrip inaccordance with one or more techniques of this disclosure.

FIG. 3G is a combined three-dimensional view and cross-sectional view ofan example multi-layer printed circuit board that may integratewaveguide layers, signal and component layers.

FIG. 4 is a conceptual and schematic block diagram illustrating anexample integrated monopulse radar system using a slot waveguide antennaarray system in accordance with one or more techniques of thisdisclosure.

FIG. 5A is a conceptual and schematic block diagram of an example radarreceive channel and radar transmitter electronics that may be used in anobstacle collision avoidance system.

FIG. 5B is a conceptual block diagram of portions of an example receivemodule illustrating multiple channels that may be part of radar receiverelectronics in accordance with one or more techniques of thisdisclosure.

FIG. 5C illustrates some of the additional components that may beincluded in the radar receiver electronics, which may be mounted andinterconnected on multi-layer printed circuit board.

FIG. 6 is a conceptual diagram illustrating an example radartransmission pattern for a collision avoidance system, in accordancewith one or more techniques of this disclosure.

FIGS. 7A-7C are conceptual diagrams illustrating example radar receivepattern for a collision avoidance system, in accordance with one or moretechniques of this disclosure.

FIG. 8 is a graph illustrating an example radar receive pattern for acollision avoidance system, in accordance with one or more techniques ofthis disclosure.

DETAILED DESCRIPTION

This disclosure describes various techniques related to collisionavoidance systems and antennas for use in such collision avoidancesystems. A collision avoidance system in accordance with the techniquesof this disclosure may use radar to detect unwanted objects in acoverage area, and in response to detecting an unwanted object in thecoverage area, send a notification to an operator. In one example, acollision avoidance system of this disclosure may be installed on anairplane, and the coverage area may be the area surrounding a wingtip ornose of the aircraft. In another example, a collision avoidance systemof this disclosure may be installed on a sea vessel, and the coveragearea may be all or a portion of the area surrounding the vessel. As willbe explained in more detail below, in order to constrain the coveragearea to a desired area that is large enough to adequately detectpotential hazards but still small enough to not yield a large number offalse positives, a radar collision avoidance system of this disclosuremay include an antenna that utilizes one or more of digital beamforming, electromagnetic band-gap isolation, a substrate integratedwaveguide (SIW), and other such features.

In some implementations, the collision avoidance system, including boththe antennas and associated electronics, may be implemented into asingle integrated package. The single integrated package may, in manyinstances, be small enough and light weight enough to be installed in avariety of locations such as in the radome at the top of the verticalstabilizer of an aircraft. Additionally, the collision avoidance systemmay communicate wirelessly with a display or user terminal such that thecollision avoidance system can be installed without the need for longwiring runs. In other examples, the collision avoidance system mayimplement other techniques to communicate with other systems, such as auser terminal, flight information system, vehicle information system,railroad or automobile traffic management system or similar. Thecollision avoidance system may communicate with others systems usingoptical, wired (e.g., Ethernet, USB, etc.), or other similar connectionsor communications mediums.

FIG. 1A is a conceptual diagram illustrating an example coverage area ofa collision avoidance system mounted on an aircraft. FIG. 1A depictsaircraft 10 with an example collision avoidance system, which may bemounted in or on vertical stabilizer 16 of aircraft 10. The examplecollision avoidance system may be configured to detect objects in a leftradar coverage area 12L and a right radar coverage areas 12R(collectively “radar coverage area 12”). Radar coverage area 12 mayinclude an area approximately 80 degrees wide. Information from thecollision avoidance system may combine with information from a weatherradar system that may be mounted in the nose radome of aircraft 10. Thefull weather radar system carried in the nose of the aircraft may beused during ground operation to cover a region between 120 and 180degrees wide from the nose location.

The example collision avoidance system may additionally be configured tocommunicate, for example via Wi-Fi, over communication area 14. Theillustration of communication area 14 represents only one example of acommunication area. Other sizes and shapes of communication areas mayalso be used. The Wi-Fi communication area 14 may be generated bycommunication circuitry within the collision avoidance system. Thecommunication circuitry may receive target detection information fromtargets detected within radar coverage area 12 and transmit targetdetection information to at least one external display withincommunication area 14. Wi-Fi coverage area may also be described awireless local area network (WLAN) datalink. The collision avoidancesystem may transmit signals within Wi-Fi communication area 14 toexternal displays within aircraft 10, or to other displays outside ofaircraft 10. For example, one or more safety observers, or “wingwalkers” helping to guide aircraft 10 during ground operations may carrydisplay units that may receive target detection information from thecollision avoidance system.

A collision avoidance system may also be installed near the passengergate at an airport to assist in guiding an aircraft to the terminal. Inthis taxi guidance example, the collision avoidance system maycommunicate with other devices, such as display devices, using wirelessor wired communication techniques.

Other example applications for the collision avoidance system mayinclude use on helicopters for collision avoidance and landingassistance in a degraded visual environment (DVE) such as blowing dustor snow. An unmanned aerial vehicle (UAV) may include a collisionavoidance system. A collision avoidance system may be mounted on a trainor at a railroad crossing to notify the train operators, or railroadtraffic management, of potential obstacles. A collision avoidance systemmay be used on a sea vessel for guidance during restricted maneuvering,such as entering or exiting port or transiting a channel or canal. Thecollision avoidance system on a sea vessel may also be used as earlywarning when faced with the risk of piracy in certain areas of theworld. Although the techniques of this disclosure will primarily bedescribed with reference to an aircraft, it should be understood thatthe techniques described herein are not limited to aircraft and can beimplemented on other types of vehicles and vessels, as well as onstationary structures as well.

FIG. 1B is a conceptual diagram illustrating a more detailed view of anexample position of a collision avoidance system mounted in verticalstabilizer 16 of aircraft 10. The example collision avoidance system mayinclude one or more integrated radar systems mounted in the verticalstabilizer 16 of aircraft 10. For example, integrated radar system 18Lmay include monopulse radar circuitry, a slotted waveguide radartransmit antenna, a slotted waveguide radar receive antenna, andexternal communication circuitry. In some examples, the variouscomponents of the collision avoidance system may be housed in a single,integrated package. Integrated radar system 18L may mount in an existingradome on top of the vertical stabilizer 16 of aircraft 10. In thisdisclosure the terms “slot waveguide” and “slotted waveguide” may beused interchangeably. The existing radome may be the same radome used bythe VHF omnidirectional range (VOR) navigation antenna. The collisionavoidance system may include two integrated radar systems 18L and 18Rmounted on the left and right sides of the existing radome, which mayprovide coverage on both sides of aircraft 10, including coverage beyondboth wingtips of aircraft 10. For example, integrated radar systems 18Land 18R may provide radar coverage area 12 as shown in FIG. 1B.

Integrated radar system 18L may be configured to avoid other structuresthat may be included in an aircraft vertical stabilizer. For example,some vertical stabilizers may include a conductive strip that is part ofa lightning strike protection system. Also, in some examples, a verticalstabilizer may include one or more antennae, such as a high frequency(HF) long range communication antenna. A collision avoidance system andintegrated radar system configured to not interfere with suchstructures, as well as configured so these structures do not interferewith the integrated radar system performance, may have advantages overother examples. In one example, integrated radar system 18L may beapproximately four inches tall, eight inches long, and one inch thick(4″×8″×1″). In other examples, such as on a UAV, the integrated radarsystem may be smaller.

Also, integrated radar system 18L may be configured to draw power fromexisting power within a vertical stabilizer with minimum modification.For example, an integrated radar system 18L may be configured to drawpower from the existing system already in place within the verticalstabilizer. As the collision avoidance system would have the largestadvantage during ground operations, such as taxiing, an integrated radarsystem that drew power from an existing system, only used on the ground,would have advantages over other examples. For example, the integratedradar system could draw power from a taxi lighting system, used onlyduring ground operations.

FIG. 2A is a conceptual and assembly diagram illustrating an explodedview of an example integrated radar system, which may be a component ofa collision avoidance system in accordance with one or more techniquesof this disclosure. FIG. 2A illustrates an example integrated radarsystem 100 which may include a SIW Tx antenna and a protective cover orshield 104. Integrated radar system 100 may, for example, be the sametype of integrated radar system as integrated radar system 18L and 18Rshown in FIG. 1B. In the example of FIG. 2A, the integrated radar systemis implemented as a multi-layer printed circuit board (PCB) 101 thatincludes an SIW antenna layer 102 and one or more circuit layers 103.Circuit layers 103 may include 8-channel receiver chips 108A-108D,analog-to-digital (A/D) converters 106A-106D as well as other circuitelements. An analog-to-digital converter may also be called an “ADC.”

Multi-layer PCB 101 may include circuits and components that implementradar transmitter electronics, radar receiver electronics, one or moreprocessors, communication electronics, power conditioning anddistribution, clock/timers and other circuitry and components. The oneor more processors may be configured to control the radar transmitterelectronics and radar receiver electronics as well as process andidentify radar targets and send notifications and information to usersusing the communication electronics. A processor may include, any one ormore of a microprocessor, a controller, a digital signal processor(DSP), an application specific integrated circuit (ASIC), afield-programmable gate array (FPGA), a system on chip (SoC) orequivalent discrete or integrated logic circuitry. A processor may beintegrated circuitry, i.e., integrated processing circuitry, and thatthe integrated processing circuitry may be realized as fixed hardwareprocessing circuitry, programmable processing circuitry and/or acombination of both fixed and programmable processing circuitry.

The SIW antenna layer 102 may be electrically connected to circuit pathsand components on one or more circuit layers 103. In some examples,plated vias may provide connections between one or more circuit layers103, as well as to SIW antenna layer 102. A via may be a plated orunplated hole that may be drilled, etched or otherwise formed betweenlayers of multi-layer PCB 101. A plated via may be plated with aconductive material to electrically connect layers. Some examples ofconductive material may include copper, solder, conductive epoxy orother materials.

Protective shield 104 may cover and provide structural support forexample integrated radar system 100. Protective shield 104 may be amolded plastic, stamped or formed sheet metal or other suitablematerial. Protective shield 104 may include a conductive coating in oneor more areas to provide shielding for electromagnetic interference(EMI). Protective shield 104 may include penetrations for power,communication or other connections as well as be configured to securelymount integrated radar system 100.

In operation, integrated radar system 100 may provide digital electronicbeam steering on received radar reflections by using, in part, phaseshift commands within the components on one or more circuit layers 103.The radar transmitter electronics, in signal communication with theradar transmit antenna, are configured to output, e.g., transmit,monopulse radar signals that are a fixed, wide beam illumination. Theradar receiver electronics in signal communication with the radarreceive antenna search the reflected radar signals by a “pencil beam”monopulse receive pattern that scans within the illuminated transmitarea. In other words, integrated radar system 100, in this example, is afrequency modulated continuous wave (FMCW) dual antenna radar systemthat provides wide beam illumination on transmit and then anelectronically scanned receive beam that searches within the widetransmit illumination area. The FMCW radar signals provide very finerange resolution and allows very low receiver bandwidth and low datarates. This includes resolution in all three dimensions. In other words,integrated radar system 100 may locate the X, Y and Z position ofpossible collision threats. Locating the height of a target may have theadvantage of reducing false alarms. For example, the collision avoidancesystem may detect an object that will pass under the wings but be at aheight that will pose no danger to the wings, engine nacelles or otherportions of an aircraft.

The digital electronic beam steering at baseband frequencies providesthe advantage of reduced cost and complexity because of fewer radiofrequency (RF) components. Digital electronic beam steering may also becapable of receiving multiple simultaneous beams.

In one example, integrated radar system 100 may use a heterodyne FMCWradar with a 16 MHz first intermediate frequency (IF) before downconversion to a baseband between 1 KHz and 2 MHz. Integrated radarsystem 100 may apply the 16 MHz offset using a dual direct digitalsynthesis (DDS) at the transmit array. A heterodyne system may provideadvantages over other FMCW radars that use a homodyne receiver todirectly convert RF signals to baseband near zero frequency. Integratedradar system 100 may include components with a passband that includes 16MHz. These components may also provide simultaneous down conversion tobase band, I/Q channel formation and four-bit phase shift. By usingmulti-function components along with frequency down conversion,integrated radar system 100 may provide advantages over a standardhomodyne receiver, even if the homodyne receiver used an I/Q mixer onreceive. In this way, integrated radar system 100 may achieveperformance advantages. A few examples include I/Q accuracy (true 90degree offset), four-bit phase shift, fine range and elevationresolution, low receiver bandwidth, low data rates, small size, lightweight, low power consumption, integrated package and easy retrofit ofexisting platforms.

FIG. 2B is a conceptual diagram illustrating the transmission, receiveand communication antennae of an example integrated radar system, whichmay be a component of a collision avoidance system in accordance withone or more techniques of this disclosure. FIG. 2B illustrates a moredetailed view of the radiating and receiving portion of SIW antennalayer 102 shown in FIG. 2A. SIW antenna layer 102 may include a Wi-Fiantenna 120, an SIW receiver (Rx) array 122, an isolation area 124 andan SIW transmit (Tx) antenna 126. SIW Rx array 122 may include one ormore radar receiver antenna subarrays 132A-132D. Each subarray mayinclude an SIW antenna device 130. In the example of FIG. 2B, eachsubarray 132A-132D contains eight SIW antenna devices. For clarity, FIG.2B only shows SIW antenna device 130 with a number. SIW antenna device130 may also be referred to as a slotted waveguide antenna device.Therefore, SIW Rx array 122 may be considered a slotted waveguide radarreceive antenna. SIW Tx antenna 126 may be considered a slottedwaveguide radar transmit antenna.

SIW Tx antenna 126 may include one or more SIW Tx antenna devices 134Aand 134B (collectively SIW Tx antenna device 134). Each SIW Tx antennadevice 134 may be similar to SIW antenna device 130 in construction andfunction. SIW Tx antenna 126 (or slotted waveguide radar transmitantenna) may be in signal communication with the radar transmitterelectronics. The radar transmitter electronics, in conjunction with theslotted waveguide radar transmit antenna, may be configured to outputradar signals to a predetermined coverage area. The predeterminedcoverage area may be similar to radar coverage area 12 shown in FIG. 1A.The terms radar transmit electronics and radar transmitter electronicsmay be used interchangeably in this disclosure.

SIW Rx array 122 (or slotted waveguide radar receive antenna) may be insignal communication with radar receiver electronics. The radar receiverelectronics may include digital beam forming circuitry configured toreceive radar reflections corresponding to the outputted radar signalsfrom the radar receive antenna. The outputted radar signals may reflectoff objects present in the predetermined coverage area. The radarreceiver electronics may send information to the one or more processorsabout the reflected signals from objects present in the predeterminedcoverage area. The one or more processors may be configured to generatea notification in response to a radar reflection received from the firstcoverage area.

Isolation area 124 may be used to isolate the outputted radar signalscoming from SIW Tx antenna 126 from interfering with SIW Rx array 122.Isolation area 124 may have dimensions and be composed of material toensure proper function of integrated radar system 100. For example,isolation area 124 may be a structure such as an electronic band gapstructure or an absorptive structure. The dimensions and/or material mayvary depending on the operating frequency of integrated radar system100.

Wi-Fi antenna 120 may be configured to transmit and receive signals usedto communicate using a wireless local area network (WLAN). Wi-Fi antenna120 may be communicatively coupled to electronic communication circuitrywithin integrated radar system 100 configured to receive informationfrom one or more processors within integrated radar system 100. Forexample, the electronic communication circuitry may be part ofmulti-layer PCB 101. The electronic communication circuitry, inconjunction with Wi-Fi antenna 120 may be configured to communicate withdisplay units or other units external to integrated radar system 100.Some examples of external display units may include tablet computers orhand-held mobile devices.

FIG. 3A is a three-dimensional view illustrating an example SIW elementin accordance with one or more techniques of this disclosure. SIWelement 131 may be a component of SIW antenna device 130 shown in FIG.2B. SIW element 131 may include a radiating slot layer 140, a first SIWportion 142, a ground layer 144 and a second SIW portion 150. SIWelement 131 may be configured to operate with a first radio-frequency(RF) energy of a first wavelength (Aλg), where Aλg is the wavelength ofthe first RF energy inside the SIW material and Aλ is the wavelength ofthe first RF energy in free space.

The first SIW portion 142 may include two or more rows of vias 152. Eachvia may be a plated via, that is, the inner surface of each via may beplated with a conductive material such as copper. Dimensions for vias aswell as spacing and relationship to slots in radiating slot layer 140will be discussed in more detail in FIG. 3D below.

Radiating slot layer 140 may form a first layer of each SIW and may beelectrically connected to, but not penetrated by each via 152. Radiatingslot layer 140 may include a plurality of slots arranged in a row ofslots 141. The row of slots 141 may run parallel to the rows of vias 152and between each row of vias. Each slot of the plurality of slots maypenetrate radiating slot layer 140. Ground layer 144 may form a secondlayer of the first SIW portion and may be electrically connected to, butnot penetrated by each via 152. Therefore, ground layer 144 may beelectrically connected to radiating slot layer 140.

Second SIW portion 150 may include two or more rows of vias 152A andmicrostrip transition 148. Second SIW portion 150 may bond to groundlayer 144. Vias 152A may electrically connect to, but not penetrateground layer 144. Therefore, vias 152A, vias 152, ground layer 144 andradiates slot layer 140 are electrically connected. Moreover, vias 152A,vias 152 may be considered ‘blind holes,’ in that the holes connect, butdo not penetrate a metal layer, such as ground layer 144. Therefore, thevias on different layers may be configured to overlap vertically. Inother words, the vias may be configured to line up with each other, butwithout physically connecting. This arrangement may have advantages in avariety of applications, because, for example, the arrangement may offerflexibility in circuit layout. Both first SIW portion 142 and second SIWportion 150 may include one or more bondply layers.

Microstrip transition 148 may have specific dimensions and shape thatdepend on the signal frequency. Microstrip transition 148 may bepositioned in relation to coupling slot 146 such that microstriptransition 148 stimulates coupling slot 146.

Coupling slot 146 may penetrate ground layer 144. Coupling slot 146 mayconnect first SIW portion 142 to second SIW portion 150. In someexamples, SIW element 131 is a receive element. Reflected radar signalsimpinging on radiating slot layer 140 may penetrate to first SIW portion142. First SIW portion 142 may guide any received RF energy from thereflected radar signals to coupling slot 146. Coupling slot 146 maycouple the RF energy further to second SIW portion 150. In otherexamples, SIW element 131 is a transmit element. Second SIW portion 150may receive RF energy from the radar transmitter electronics and couplethe RF energy to first SIW portion 142 through coupling slot 146.

Terminal edge 154 may penetrate second SIW portion 150, ground layer 144and first SIW portion 142. The example of FIG. 3A depicts terminal edge154 as a slot passing between the layers. In this example, the slot maybe plated with a conductive material, such as copper. The long edge ofterminal edge 154 may be perpendicular to the row of vias 152. Terminaledge 154 may electrically connect, but not penetrate radiating slotlayer 140. Therefore, terminal edge 154 may electrically connectradiating slot layer 140 to ground layer 144. Specific dimensions forterminal edge 154, spacing and physical location relative to otherfeatures of SIW element 131 will be discussed in more detail below, suchas FIG. 3D.

The SIW may be constructed of copper clad PCB for the upper and lowerwaveguide surface, with the dielectric of the PCB for the waveguidevolume and plated vias (aka holes) for the waveguide walls. In otherwords, SIW is a transmission line that creates a waveguide within asubstrate. Its waveguide consists of two lines of holes as the wall ofrectangular waveguide and the metallic layer on the top and bottom toform a rectangular cavity. The SIW waveguide suffers higher insert lossthan aluminum waveguide caused by (a) the substrate, (b) the gap betweenholes and (c) the surface roughness between metallic layer and thesubstrate. But it brings a lot of advantages to develop radar systemsuch as mono-pulse radar that generally requires 4 antenna beams. Someadvantages include, SIW makes the rectangular waveguide very thin andlight, it benefits many mechanically steered antennas as its lowerweight and relatively small moment of inertia. An SIW antenna is a PCBversion of a slotted waveguide antenna. An SIW antenna may haveadvantages over other types of slotted waveguide antennae, such as aslotted waveguide antennae constructed from aluminum. For example, thesubstrate filled in SIW structure makes it is possible to put more slotsin one branch, thereby the SIW antenna array is able to offer a tight,narrow beam-width that is beneficial to many applications.

Some examples of SIW monopulse antenna array may have many difficulties.These may include the strong mutual coupling between slots, thedifficulty in layout and positioning, the complex estimation of itsequivalent guide wavelength and the difficulty of consistentmanufacture, along with other difficulties. SIW antennae using thetechniques of this disclosure may result in a SIW monopulse antennaarray that is highly integrated, highly shielded, easy to manufactureand reliable.

FIG. 3B illustrates a section of an example slot waveguide antenna arraysystem with a separate mixer for each channel. FIG. 3B illustratesexample SIW element 131 along with additional components, which may bepart of an integrated slot waveguide antenna array system. As shown inFIG. 3A, SIW element 131 may include radiating slot layer 140, first SIWportion 142 and second SIW portion 150. Other components of SIW element131, such as ground layer 144, omitted for clarity. FIG. 3B depictsadditional elements including mixer 164 and third SIW portion 158. FIG.3B also depicts an example cross section 160 of an example SIW antennadevice and antenna subarray layout 162. Example cross section 160illustrates radiating slot layer 140, first SIW portion 142, groundlayer 144, a signal layer and an additional substrate and ground layer.Example cross section 160 illustrates a four-layer PCB, with a slotlayer, a ground layer, a signal layer and a second ground layer withsubstrate in between each metal layer. In other examples, cross section160 may illustrate a three-layer, five-layer or more layers.

Antenna subarray layout 162 may include eight SIW antenna devices,similar to SIW antenna device 130 shown in FIG. 2B. Each SIW antennadevice may be dedicated to a separate radar channel. Antenna subarraylayout 162 may also include a mixer 164A for each device/channel and aneight-way power divider (PD) 176. Example of antenna subarray layout 162illustrates eight-way power divider 176 as laid out on the signal layer,as shown in cross section 160. Eight-way power divider 176 may beconfigured so each path length from the local oscillator (LO) is thesame length. This may ensure the signal from the LO, such as a voltagecontrolled oscillator (VCO), arrives at each mixer 164A at the same timeand with the same phase.

Third SIW portion 158 may include vias 152C and two microstriptransitions 148A and 148B. Vias 152C may be a different diameter andspacing than vias 152 and be configured to operate at a different RFenergy than that used by the first SIW portion and the second SIWportion. Third SIW portion 158 may be configured to operate with an RFenergy of a different wavelength and frequency. Third SIW portion 158may connect mixer 164 to eight-way power divider 176 depicted in antennasubarray layout 162. The area of third SIW portion 158 may provide spacefor a signal transfer area 165. Signal transfer area 165 may carrysignals such as output of mixers 164, control signals and other signals.Signal transfer area 165 may also include electronic components that mayinteract with signals carried by signal traces on signal transfer area165. In one example, not shown in FIG. 3B, the output of mixers 164 mayreach the signal transfer area using conductive vias different anddistinct from vias 152, 152B or 152C. In the example of FIG. 3B, thepower divider is on a metal layer of multi-layer PCB 101, rather than awaveguide, as may be found in other examples. A power divider on themetal layer may provide advantages in cost, manufacturability,reliability as well as allow a smaller size for the radar system.

FIG. 3C illustrates a section of an example slot waveguide antenna arraysystem with a four-channel mixer and single SIW portion connecting themixer to a power divider and a local oscillator (LO). FIG. 3C may besimilar to FIG. 3B except instead of a separate mixer for each channel,the example of FIG. 3C depicts a four-channel mixer 172 and 172A. FIG.3C also depicts an example antenna subarray layout 170 with eightantenna devices/channels, similar to antenna subarray layout 162, exceptexample of FIG. 3C connects the LO to two four-channel mixer componentsand therefore only needs the two-way PD. The two-way PD shown in FIG. 3Coperates to connect the local oscillator (LO) to mixer 172, similar tothe eight-way PD 176 for FIG. 3B. Because the example of FIG. 3Cincludes fewer mixers and fewer PD circuit traces, this may allow morespace on the layers above and below third SIW portion 168 for additionalcomponents and/or space for additional circuit traces or components. Inother words, because third SIW portion 168, which may include SIWelements 174A and 174B, may be larger than the similar third SIW portion158, signal transfer area 165A may be larger than the similar signaltransfer area 165. This may allow additional space for components or fortraces to carry signals, for example in hardware component region 166.The terms “circuit trace”, “trace” or “circuit path” may be usedinterchangeably in this disclosure.

Similar to the layout for eight-way power divider 176 shown in FIG. 3B,FIG. 3C illustrates example two-way power divider 176A with equal lengthpaths. This may ensure the signal from the LO, such as a VCO, arrives ateach mixer 172A at the same time and with the same phase.

FIG. 3D is a two-dimensional view of an example SIW element illustratingdimensions and spacing in accordance with one or more techniques of thisdisclosure. FIG. 3D depicts a SIW defined by rows of plated vias orholes 152D. In this disclosure hole, plated hole, via and plated via maybe used interchangeably, unless otherwise specified. FIG. 3D defines thespacing between centerline of adjacent holes in each row to besubstantially equal, where substantially equal means equal withinmanufacturing tolerances. In other words, the spacing between adjacentholes in the same row is equal, plus or minus any variations inmanufacturing. For example, d1=d2 as shown in SIW power divider 190.Note that SIW power divider 190 is different from the eight-way PD 176and two-way PD 176A described above. SIW power divider 190 is a powerdivider implemented in SIW material and construction. The eight-way PDand two-way PD described above are implemented on a circuit layer orsignal layer and may be of metal or other conductive material. SIW powerdivider 190 is another example of an SIW layout in accordance with thetechniques of this disclosure. SIW power divider 190 is not shown inFIGS. 3A-3C.

The equal distance between hole centerline d1 and d2 may be dividedevenly by ¼ equivalent guide wavelength according to the equation (N*d=¼λg). In the example of FIG. 3D, the equal hole spacing may be defined as⅛ λg. In other words, the via spacing may be selected to operate for aparticular wavelength/frequency of RF energy. Therefore, for each row ofvias 152D, a centerline of each via in the first row of vias may be ½Aλg from the centerline of an adjacent via in the first row of vias.Similarly, a centerline each via in the second row of vias of may be ½Aλg from the centerline of an adjacent via in the second row of vias.

The example of FIG. 3D defines the SIW waveguide width (a) as evenmultiple of the equal distance (d) between the centerlines of each rowof vias according to the equation a=(2n)*d. For example, selecting n=3results in an SIW width a=6d (182). Selecting the SIW width a=6d resultsin a hole 183 in the center of the short edge, as shown in SIW powerdivider 190. This may have performance advantages over other selections.As shown in FIG. 3D, the first row of vias is substantially parallel tothe second row of vias and a centerline of the first row of vias is ¾Aλg=6d (182) from a centerline of the second row of vias. Here,substantially parallel means parallel within manufacturing tolerances.In other words, the centerline of the first row is parallel to thecenterline of the second row, plus or minus any variations inmanufacturing.

Variations and tolerances apply throughout this disclosure. For example,SIW width 182 described above as a=6d should be understood to meana=6d±tolerances from manufacturing or other sources.

FIG. 3D also depicts a row of radiating slots. By selecting the length,spacing and position of each radiating slot in the row of radiatingslots, the reflection around each slot can be the same, that is, byrepeating four holes for each ½ λg (181). FIG. 3D depicts finalradiating slots 184A-184C in the row of radiating slots. In other words,selecting each radiating slot to have the same length and spacing, andplacing a long-edge centerline of the final radiating slot, such as184C, to be ¼ Aλg from the terminal edge 186C may result in a four-space(4d) reflection zone from the plated vias on either side of eachradiating slot. FIG. 3D depicts this four-space reflection zone by theitem 181, which shows 4d e.g. four equal spaces between holes, fromcenterline to centerline along the radiating slots.

Similarly, for alternative examples of terminal edges 186A (a row ofvias) and 186B (a plated slot), placing final radiating slots 184A and184B so the long-edge centerline of the final radiating slot is ¼ Aλg(188) from the terminal edge may result in a four-space reflection zone(181) for the radiating slots. The row of vias terminal edge, as shownby 186A may have inaccuracies if the wavelength is not precisely matchedto the dimensions. This is because the equivalent distance from thecenter of the last slot to the “edge” for a row of vias is actuallysmaller than ¼ λg. At millimeter-wave frequency band, this may causeundesirable results. In some examples a plated slot (186B) or edgeplating (186C) may have advantages over the row of vias shown in 186A.An SIW slot waveguide antenna according to the techniques of thisdisclosure may have advantages for consistent and reliable SIW designand performance.

FIG. 3E is a three-dimensional view of an example SIW power divider.FIG. 3E depicts example SIW power divider 190, which is configured thesame as SIW power divider 190 shown in FIG. 3D. Example, SIW powerdivider 190 as depicted by FIG. 3E includes vias 152D, an SIW width a=6d(182), which results in a hole 183 in the center of the short edge. FIG.3E also depicts three microstrip transitions, though for clarity onlymicrostrip transition 148C is labeled. FIG. 3E illustrates athree-dimension view of an example implementation of an SIW powerdivider. SIW power divider is distinct from power dividers 176 and 176Ain that power dividers 176 and 176A may be implemented on a circuitlayer of an example multi-layer PCB 101, where SIW power divider 190 maybe implemented on an SIW layer.

FIG. 3F is a two-dimensional view of an example slot waveguide antennaarray system illustrating dimensions for a coupling slot and microstripin accordance with one or more techniques of this disclosure. Eachchannel may have a coupling slot 146E. The distance between theshort-edge centerline of coupling slot 146E to terminal edge 154E may begiven according to the equation:

$D_{c} = {\frac{n}{2}\lambda\;{g\left( {{n = 1},2,{3\mspace{14mu}\ldots\mspace{14mu}{To}\mspace{14mu} N}} \right)}}$The example of FIG. 3F depicts terminal edge 154E as a plated slot. Thedistance between microstrip transition 148E and terminal edge 154E maybe given according to the equation:

$D_{T} = {\frac{n + 1}{2}\lambda\;{g\left( {{n = 1},2,{3\mspace{14mu}\ldots\mspace{14mu}{To}\mspace{14mu} N}} \right)}}$For a digital active phased array, a longer D_(c) and D_(T) suffershigher insert loss than a shorter D_(c) and D_(T). However, a largerD_(c) and D_(T) provides additional space to put additional componentson other layers. In other words, n>1, provides more space for additionalcomponents. The example of FIG. 3F depicts n=1 to minimize insertionloss resulting in D_(c)=λg/2 and D_(T)=λg. An SIW slot waveguide antennawith coupling slot location and microstrip location according to thetechniques of this disclosure may have advantages for consistent andreliable SIW design and performance. The layout and benefit ((2n−1)/N−1coupling) may balance loss and enough area for the back circuit. Asdepicted in the example of FIG. 3F, the terminal of each SIW elementconnects to a ground layer, e.g. ground layer 144, using a single platedslot hole (186B) instead of many vias or holes (186A), as shown in FIG.3D.

FIG. 3G is a combined three-dimensional view and cross-sectional view ofan example multi-layer PCB that may integrate waveguide layers, signaland component layers. FIG. 3G includes example cross-sectional view 195with three-dimensional views of first SIW portion 142B and third SIWportion 158B. In the example of FIG. 3G, first SIW portion 142B andthird SIW portion 158B are configured the same as the example first SIWportion 142 and third SIW portion 158 as shown in FIG. 3B.

Cross section view 195 includes substrate layers 196A-196D and, thoughnot labeled for clarity sake, may also include metal layers described inFIG. 3B, e.g., a slot layer, a ground layer, a signal layer and a secondground layer. The portion of example multi-layer PCB illustrated bycross-section 195 includes RF front end 198, third SIW portion 158A withvias 152C, first SIW portion 142A with vias 152 and radiating slot layer140. The vias, and radiating slot layer 140, are configured in theexample of FIG. 3G the same as in the example of FIG. 3B, and otherfigures described above. Coupling slot 146B connects first SIW portion142A to substrate layer 2 (196B). In some examples, multi-layer PCB 101may include additional coupling slots between other layers. Microstriptransition 148D and 148E provide a connection between the SIW and thesignal layer and function the same as microstrip transition 148described above.

FIG. 4 is a conceptual and schematic block diagram illustrating anexample integrated monopulse radar system using a slot waveguide antennaarray system in accordance with one or more techniques of thisdisclosure. FIG. 4 depicts SIW Rx array element 200 and SIW Tx array202, which function similarly to the SIW Rx array 122 and SIW Tx antenna126 as shown in FIG. 2B. Rx mixer 204 operates in a manner similar tomixer 164 from FIG. 3B. Reference signal 218 may be a local oscillator(LO) signal that may pass through a similar eight-way divider as shownin FIG. 3B. Receiver IC 206 and ADCs 212A-212D may be similar to thereceiver chip 108A-108D and A/D converters 106A-106D shown in FIG. 2A.An example component that may perform some of the features of receiverIC 206 may include the AD9670 Octal Ultrasound Analog Front End (AFE)Receiver, which will be described in further detail below.

Rx mixer 204 may receive inputs from SIW Rx array element 200 andreference signal 218 from digital synthesizer transmitter 216 todown-convert the reflected radar signals received by SIW Rx arrayelement 200. Rx mixer 204 may output the downconverted radar receivesignal to a respective receiver integrated circuit (IC) 206 for arespective receive channel. Receiver IC 206 may output the respectivesignals for the respective receive channel to a respective ADC, such asADC 212C as shown in the example of FIG. 4.

FPGA processor and controller 214 (“FPGA 214”) may receive the digitizedsignals from the different receive channel ADCs 212A-212C. FPGA 214 mayperform the functions of digital receive beam steering, target detectionprocessing and analysis and send target information to the externalcommunication system to be further sent to one or more display devices.For example, FPGA 214 may control the radar transmitter electronics,which are configured to output radar signals in conjunction with the SIWradar transmit array 202. Radar transmitter electronics may includedigital synthesizer transmitter 216.

FPGA 214 may also control the radar receiver electronics which mayinclude Rx mixer 204, the four receiver integrated circuits (IC) 206,summing amplifier 210 and ADCs 212A-212D. The radar receive electronicsmay include digital beam forming circuitry configured to receive radarreflections corresponding to the outputted radar signals, and to sendsignals associated with the radar reflections to FPGA 214. SIW Rx arrayelement 200, acts as a radar receive antenna to collect radarreflections impinging on the surface of its slot layer. SIW Rx arrayelement 200 may be a single SIW antenna device 130 in a subarray 132Awithin the SIW Rx array 122, as depicted in FIG. 2B. The terms radarreceive electronics and radar receiver electronics may be usedinterchangeably in this disclosure.

FPGA 214 and digital synthesizer transmitter 216 may include circuitrythat converts received radar signals to a lower frequency for furtherprocessing. Further processing may include beam steering, targetdetection and location as well as other functions. Other types offunctions performed by FPGA 214 and digital synthesizer transmitter 216may include in-phase and quadrature processing (I and Q), filtering,frequency, phase and amplitude control, modulation, direct digitalsynthesis (DDS) and other functions. The digital beam forming mayinclude heterodyne processing. The digital beam forming circuitry may beconfigured to operate in the ultrasonic frequency range.

FIG. 5A is a conceptual and schematic block diagram of an example radarreceive channel and radar transmitter electronics that may be used in anobstacle collision avoidance system. The example diagram of FIG. 5Adepicts a single receive channel and an example implementation ofsuperheterodyne up and down converting from RF frequencies to otherfrequencies. Other receive channels that may be part of a collisionavoidance system are not shown in FIG. 5A for clarity.

FIG. 5A includes additional details of portions of integrated radarsystem 100 using a slot waveguide antenna array shown in FIG. 4. FIG. 5Amay include SIW Rx array element 200, SIW Tx array 202 and Rx mixer 204as shown in FIG. 4. Addition components shown in FIG. 5A may be includedin FPGA processor and controller 214, digital synthesizer transmitter216 and Receiver IC 206. FIG. 5A depicts VCO 300, local oscillator (LO)feed network 302 and other receive channels 304, along with in-phase andquadrature (I and Q) unit 306, low pass filters (LPF) 308 and 312 andanalog to digital converters 310 and 314. Other radar electronics mayinclude FPGA 214A, synthesizer 322, 128 MHz master clock 324, frequencydividers 326, dual digital direct synthesis (DDS) unit 328, I/Q singleside band (SSB) mixer 330, and amplifier 332. Also Wi-Fi system 320,which may receive information from FPGA 214A.

The radar receiver electronics depicted in FIG. 5A down-convert receivedradar signal from SIW Rx array element 200 to an intermediate frequency(IF) 16 MHz (340) and to lower frequencies for further processing, whichmay include receive beam steering. The radar transmitter electronics maytransmit RF energy with a wide azimuth and narrow elevation throughtransmit (Tx) array 202.

VCO 300, as shown in the example of FIG. 5A, generates a 24 GHz signalwhich is distributed to the LO feed network 302 and further to Rx mixer204. LO feed network 302 may function, for example, as an eight-waypower divider 176 or two-way power divider 176A as shown in FIGS. 3B and3C. VCO 300 also distributes 24 GHz to I/Q SSB mixer 330. VCO 300 mayreceive input from synthesizer 322. 24 GHZ is shown as one example. Inother examples VCO 300 may generate other frequencies, such as 13 GHz.

LO Feed network 302 may output the 24.0 GHz LO signal to other receivechannels 304 as well as Rx mixer 204, which functions the same as Rxmixer 204 shown in FIG. 4. In the example of FIG. 5A, Rx mixer 204converts the 24.016 GHz reflected radar signal from SIW Rx array element200 to an intermediate frequency (IF) of 16 MHz (340). These frequencyvalues are only for illustration. Integrated radar system 100 may alsouse other frequencies. Rx mixer 204 may output the IF of 16 MHz (340) toI and Q unit 306.

Synthesizer 322 may utilize a method of changing the division ratiowithin a digital PLL synthesizer to provide frequencies that are notintegral multiples of the comparison frequency. A divider may take afractional division ratio rather than an integer ratio by alternatingbetween division ratios. One example may include a fractional Nsynthesizer that uses the basic digital PLL loop. Analog Devicescomponent ADF4159, a direct modulation fractional-N frequencysynthesizer, is one example of a fractional N synthesizer. However, insome examples fractional N synthesizers may generate spurious signalsthat appear as false targets in the receiver. Other example ofsynthesizer 322 may include a direct digital synthesizer that may haveadvantages over a fractional N synthesizer.

Frequency synthesis may use various forms of Direct Digital Synthesizer,Phase Lock Loop, frequency multiplier and other methods. Synthesizer 322will generate a linear FMCW waveform and may receive control and otherinputs from FPGA 214A.

I and Q unit 306 may include a phase shift function along with thein-phase and quadrature function. A monopulse radar may need to getinformation both from the real and imaginary portions of the returnedradar signal. I and Q unit 306 may provide a representation of thereturned radar signal at the intermediate frequency (IF) of 16 MHz, asshown in FIG. 5A. These frequencies listed in FIG. 5A are just forillustration. Other frequencies may also be used. The quadrature downconversion may divide the 128 MHz oscillator signal by eight, e.g. 8×16MHz=128 MHz. Terms for 128 MHz master clock 324 may include referenceoscillator, 128 MHz oscillator and 128 MHz clock. These terms may beused interchangeably in this disclosure.

I and Q unit 306 may perform two functions simultaneously. First, I andQ unit 306 may divide 128 MHz clock signal 324 by eight and provide afour-bit phase shift with digital control. At the same time as thefour-bit phase shift, I and Q unit 306 may form the in-phase (I) andquadrature (Q) signal portions and downconvert the 16 MHz IF frequencyto a base band between 1 kHz and 2 kHz. The I and Q signal portions mayalso be called the “I” channel and “Q” channel. The output signal from Iand Q unit 306 passes through LPF 308 and 312 and ADCs 310 and 314 maydigitize each portion of the returned signal. ADCs 310 and 314 mayreceive input from frequency dividers 326. Both frequency dividers 326and I and Q unit 306 may receive a 128 MHz clock signal from 128 MHzmaster clock 324. Frequency dividers 326 may output a signal to ADCs 310and 314.

FPGA 214A may receive the separate I and Q signals from each receiverchannel. FPGA 214A may combine and process the signals, includingdigital receive beam steering to determine the 3D position of obstacleswithin the radar coverage area, as shown in FIG. 1A. FPGA 214A mayprocess obstacle information, including size, height, rate of closureand other information and send to Wi-Fi system 320. Wi-Fi system 320 mayfurther send obstacle information of one or more display devices. Onepossible example of FPGA 214A may include the Xilinx XC7k70t 7-seriesFPGA.

Radar transmitter electronics may include dual DDS 328 and I/Q SSB mixer330. Dual DDS 328 may receive commands and control inputs from FPGA 214Aand output a 16 MHz intermediate frequency I signal 334 and Q signal 336to I/Q SSB mixer 330. An example dual DDS may include the Analog DevicesAD9958.

I/Q SSB mixer 330 may receive the signals from dual DDS 328, as well asa 24 GHz signal from VCO 300. I/Q SSB mixer 330 may output radar signalsto amplifier 332 and further to SIW transmit array 202. One example ofamplifier 332 may include the HMC863 from Analog Devices. SIW transmitarray 202 may output the radar signals in the prescribed pattern. Anyreflected radar signals may impinge on SIW Rx array element 200 and beconducted to the FPGA for processing.

FIG. 5B is a conceptual block diagram of portions of an example receivemodule illustrating multiple channels that may be part of radar receiveelectronics in accordance with one or more techniques of thisdisclosure. FIG. 5B illustrates example components and techniques toprocess received radar signals from a portion of SIW receiver array 122as shown in FIG. 2B. The example of FIG. 5B depicts other details of thefunctions of FIG. 4 and FIG. 5A that include an example radar receiversubarray 132A, such as that shown in FIG. 2B. A complete, integratedradar system may use one or more sets of the components shown in FIG.5B. For example, an integrated radar system that uses four radarreceiver subarrays may use four sets of components as shown in FIG. 5Bto achieve the 32 channels shown in FIG. 2B.

Receive module 350 may include radar receiver antenna subarray 132A, VCO300, an Rx mixer 204A-204H for each channel, an octal analog front end(AFE) receiver 352, a summing operational amplifier (opamp) and LPF forboth in-phase 354 (“I”) and quadrature 356 (“Q”) signals, a dual channellow voltage differential signaling (LVDS) unit 358, FPGA clock dividers360 and voltage regulators 362. The components depicted in receivemodule 350 may be mounted and inter-connected on multi-layer PCB 101that includes a, SIW antenna layer 102 and one or more circuit layers103, shown in FIG. 2A.

The example of FIG. 5B depicts radar receiver antenna subarray 132A toinclude eight SIW Rx array elements 200A-200H. In other examples, radarreceiver subarray 132A may include more or less than eight SIW Rx arrayelements. Each SIW Rx array element 200A-200H connects to a respectiveRx mixer 204A-204H. Each Rx mixer 204A-204H for each of the eightchannels depicted in receive module 350 also receive a 24 GHz LO signalfrom VCO 300. The Rx mixers down-convert the reflected radar signalreceived by the SIW Rx array element for each channel and send the inputto octal AFE receiver 352. The signal path for each channel may includecomponents other than Rx mixers 204A-204H, as depicted by FIGS. 4, 5Aand below in FIG. 5C. The example of FIG. 5B depicts an Rx mixer 204 foreach channel. Other examples may use a four-channel mixer rather than asingle mixer for each channel. Example four-channel mixer components mayinclude the ADF5904 from Analog Devices. As described above, mixercomponents may have performance advantages when placed in the middle ofthe SIW subarrays so that the path lengths between each subarray and thefour-channel receiver chip is equal length. For example, this may allowthe signal from VCO 300 to arrive at the same time and in the same phasefor each receiver channel.

Octal afe receiver 352 may perform a variety of functions for each ofthe eight channels. Some examples may include preamplification, harmonicrejection, anti-alias filtering, I/Q demodulation and phase rotation,digital demodulation and decimation as well as conversion to digitalsignals through ADC. One possible example component to perform at leastsome of the functions of octal afe receiver 352 may include the AnalogDevices AD9670 Octal Ultrasound Analog Front End (AFE) Receiver. Octalafe receiver 352 may receive a 128 MHz clock input from 128 MHz masterclock 324. Octal afe receiver 352 may output an in-phase “I” signal foreach channel to a set of summing opamp and low pass filters for eachchannel, depicted as a single unit 354 in the example of receive module350. Similarly, Octal afe receiver 352 may output a quadrature “Q”signal for each channel to a set of summing opamp and low pass filtersfor each channel, depicted as a single unit 356.

LVDS unit 358 may receive the “I” and “Q” inputs from summing opamp andlow pass filters 354 and 356 as well as an input from FPGA clockdividers 360. LVDS unit 358 may operate under the LVDS, or TIA/EIA-644technical standard to sample the input signals and performanalog-to-digital conversion. Example components that may perform one ormore functions of LVDS unit 358 may include Analog Devices AD7357 orAD7356 differential input ADC components. LVDS unit 358 may output thedigitized “I” and “Q” signals for further processing, such as beamforming, obstacle identification and other functions as needed by acollision avoidance system, in accordance with one or more techniques ofthis disclosure.

Receive module 350 may also include voltage regulators 362. Voltageregulators 362 may provide regulated power supplies to the components ofreceive module 350. For example, LVDS unit 358 may require an inputvoltage of 2.5V while octal AFE receiver 352 may require an inputvoltage of 3.0 V. Voltage regulators 362 may supply power for properoperation of each component in receive module 350.

FIG. 5C is a conceptual and schematic diagram depicting additionaldetails of a portion of the radar receive electronics that may beincluded in an integrated radar system. FIG. 5C depicts four channels ofexample radar receive electronics for clarity. In the example SIWreceiver array 122 as shown in FIG. 2B, the set of electronics depictedin FIG. 5C would be repeated for the total number of channels in thereceive array. FIG. 5C retains the same numbers for components wherecomponents in FIG. 5C are the same as in other figures. For example, SIWRx array elements 200A-200D and 128 MHz master clock 324 are the same asthose components shown in FIG. 5B.

FIG. 5C illustrates some of the additional components that may beincluded in the radar receiver electronics, which may be mounted andinterconnected on multi-layer PCB 101. FIG. 5C depicts LO feed network302A, Rx mixers 204A-204D, SIW Rx array elements 200A-200D, intermediatefrequency (IF) low-noise amplifier (LNA) and high pass filter (HPF) 370,octal AFE receiver 352, summing opamp and LPF 354 and 356 for the “I”and “Q” signals, “I” ADC 314A and “Q” ADC 310A. Also shown in theexample of octal AFE receiver 352 is quadrature divider 372 and serialdata in (SDI) controller 374.

LO feed network 302A may deliver a 24 GHz oscillator signal to Rx mixers204A-204D. LO feed network 302A may receive as input the 24 GHz LOsignal from a VCO, such as VCO 300, not shown in FIG. 5C, but shown in5A. The example of FIG. 5C depicts LO feed network 302A configured soeach path length from the local oscillator (LO) is the same length. Thismay ensure the signal from the LO, such as a VCO, arrives at each Rxmixer 204A-204D at the same time and with the same phase. This issimilar to eight-way power divider 176 shown in FIG. 3B.

Rx mixers 204A-204D function the same as described above by receivingand downconverting the reflected radar signals from SIW Rx arrayelements 200A-200D. Rx mixers 204A-204D output the downconverted signalsto the respective channels of IF LNA and HPF 370 (referred to as “LNA370” for clarity). LNA 370 outputs each channel to a respective channelof octal AFE receiver 352. In the example of an FMCW radar, the highpass filter may set the frequency response of the receiver. A high passfilter is used to set the IF response to have a 40 dB per decaderesponse over a frequency range of about 1 KHz to 2 MHz. This functionexactly offsets the propagation losses as a function of range.

Octal AFE receiver 352 functions the same as described above. Alsodepicted in FIG. 5C is quadrature divider 372, which helps with thephase shift function that creates the “Q” output for the monopulse radarreceive signals. SDI controller 374 may help manage the data flow to thesumming op amps.

Summing opamp and LPF 354 and 356 may act as summing amplifier for the“I” and “Q” signals respectively. Summing opamp and LPF 354 and 356 maycombine the signals from the various receive channels for furtherprocessing. The LPF portion may remove the upper sideband from the I/Qmixing function.

“I” ADC 341A and “Q” ADC 310A perform the same function for the I and QADCs described above. “I” ADC 341A and “Q” ADC 310A digitize the fourchannels of downconverted and filtered radar receive channels and outputthe digitized signals for further processing, as described above.

FIG. 6 is a conceptual diagram illustrating an example radartransmission pattern for a collision avoidance system, in accordancewith one or more techniques of this disclosure. FIG. 6 includes anexample transmit antenna 400, a wide azimuth, narrow elevation maintransmission beam 404 and sidelobes 402. The radar transmitterelectronics, in conjunction with the radar transmit antenna 400, may beconfigured to output radar signals comprising a transmitted radarbeamwidth of less than eight degrees in elevation and at least 65degrees in azimuth. Radar transmit antenna 400 may function in a similarmanner to SIW transmit array 202 shown in FIG. 4 and SIW Tx antenna 126shown in FIG. 2B. The example SIW transmit pattern may include lowelevation sidelobes, which may have the advantages of preventing falsealerts and erroneous detections.

FIGS. 7A-7C are conceptual diagrams illustrating example radar receivepattern for a collision avoidance system, in accordance with one or moretechniques of this disclosure. FIG. 7A includes an example slottedwaveguide radar receive antenna 122A, which is similar to the SIW Rxarray 122 shown in FIG. 2B. FIG. 7B depicts an example receive radarpattern with main receive lobe 410B and side lobes 412B. FIG. 7C depictsa side view of an example radar receive pattern including main lobe410C, side lobes 412C and rear lobe 414. The beam steering radar receivepattern may include a target detection radar imaging resolution of atleast three square meters at a range of 100 meters. The receive patternmay include a radar range resolution of at least 1 meter and radarangular resolution is no more than one and one-half degrees in azimuthand elevation.

FIG. 8 is a graph illustrating an example radar receive pattern for acollision avoidance system, in accordance with one or more techniques ofthis disclosure. The graph of FIG. 8 depicts a radar receive patternsimilar to the patterns shown in FIGS. 7B-7C. FIG. 8 depicts main lobe410D and side lobes 412D.

Various examples of the disclosure have been described. These and otherexamples are within the scope of the following claims.

The invention claimed is:
 1. An obstacle detection system comprising: anintegrated radar antenna, the integrated radar antenna comprising amulti-layer circuit board, the multi-layer circuit board comprising: aslotted waveguide radar transmit antenna; a slotted waveguide radarreceive antenna; radar transmitter electronics in signal communicationwith the slotted waveguide radar transmit antenna, wherein the radartransmitter electronics: are on a layer of the multi-layer circuit boarddifferent from the slotted waveguide radar transmit antenna and theslotted waveguide radar receive antenna, and in conjunction with theslotted waveguide radar transmit antenna, are configured to outputmonopulse radar signals comprising a fixed transmitted radar pattern;radar receiver electronics in signal communication with the slottedwaveguide radar receive antenna, wherein the radar receiver electronicsinclude digital beam forming circuitry configured to receive, from theradar receive antenna, radar reflections corresponding to the outputtedmonopulse radar signals, and wherein the radar receiver electronics areconfigured to convert the received radar reflections to an ultrasonicfrequency range and to perform signal processing on the converted,received radar reflections in the ultrasonic frequency range, whereinthe ultrasonic frequency range is a passband that includes sixteenmegahertz; and one or more processors configured to generate anotification of target detection information based on the converted,received radar reflections.
 2. The obstacle detection system of claim 1,wherein the monopulse radar signals comprise a frequency modulationcontinuous wave (FMCW) waveform.
 3. The obstacle detection system ofclaim 1, wherein the slotted waveguide radar transmit antenna andwherein the slotted waveguide radar receive antenna each comprise asubstrate integrated waveguide (SIW) antenna.
 4. The obstacle detectionsystem of claim 1, wherein the radar transmitter electronics areconfigured to output the monopulse radar signals to a first coveragearea, and wherein the radar receiver electronics are configured toreceive the radar reflections off of objects present in the firstcoverage area, and wherein the one or more processors are configured togenerate the notification in response to a radar reflection receivedfrom the first coverage area.
 5. The obstacle detection system of claim1, wherein the one or more processors are further configured to generatethe target detection information in response to detecting a targetwithin a three-dimensional volume defined by a range, an azimuth and anelevation with respect to the integrated radar antenna.
 6. The obstacledetection system of claim 1, wherein the radar receiver electronicsfurther comprise a heterodyne FMCW radar with a first intermediatefrequency (IF) before down conversion to a base band.
 7. The obstacledetection system of claim 1, wherein a radar imaging resolution of thetarget detection information is at least three square meters at a rangeof 100 meters.
 8. The obstacle detection system of claim 1, wherein aradar range resolution of the target detection information is at least 1meter and a radar angular resolution of the target detection informationis no more than one and one-half degrees in azimuth and elevation. 9.The obstacle detection system of claim 1, further comprising externalcommunications circuitry configured to communicate over a wireless localarea network (WLAN) datalink.
 10. The obstacle detection system of claim1, wherein the radar transmitter electronics are operatively coupled toa first substrate integrated waveguide and the radar receiverelectronics are operatively coupled to a second substrate integratedwaveguide.
 11. The obstacle detection system of claim 1, wherein thedigital beam forming comprises heterodyne processing and the digitalbeam forming circuitry is configured to operate in the ultrasonicfrequency range.
 12. The obstacle detection system of claim 1, whereinthe radar transmitter electronics, in conjunction with the radartransmit antenna, are further configured to output monopulse radarsignals comprising a transmitted radar beamwidth of less than eightdegrees in elevation and at least 65 degrees in azimuth.
 13. Theobstacle detection system of claim 1, wherein the radar transmitterelectronics, in conjunction with the radar transmit antenna, are furtherconfigured to output the fixed transmitted radar pattern having agreater extent in azimuth than elevation, and wherein the digital beamforming circuitry is configured to electronically scan receive beamsthat search within a transmit illumination area of the beam fixedtransmitted radar pattern.
 14. The obstacle detection system of claim 1,wherein the slotted waveguide radar transmit antenna, the slottedwaveguide radar receive antenna, and the external communicationcircuitry comprise a single, integrated package.
 15. The obstacledetection system of claim 14, wherein the integrated package isconfigured to install in a radome of an aircraft vertical stabilizer.16. The obstacle detection system of claim 14, wherein the integratedpackage is configured to draw power from an existing aircraft systemthat is used during ground operations.
 17. An aircraft comprising: afirst wing; and an obstacle detection system, wherein the obstacledetection system comprises: an integrated radar antenna, the integratedradar antenna comprising a multi-layer circuit board, the multi-layercircuit board comprising: a slotted waveguide radar transmit antenna; aslotted waveguide radar receive antenna; radar transmitter electronicsin signal communication with the slotted waveguide radar transmitantenna, wherein the radar transmitter electronics: are on a layer ofthe multi-layer circuit board different from the slotted waveguide radartransmit antenna and the slotted waveguide radar receive antenna, and inconjunction with the slotted waveguide radar transmit antenna, areconfigured to output monopulse radar signals comprising a fixedtransmitted radar pattern; radar receiver electronics in signalcommunication with the slotted waveguide radar receive antenna, whereinthe radar receiver electronics include digital beam forming circuitryconfigured to receive, from the radar receive antenna, radar reflectionscorresponding to the outputted monopulse radar signals, and wherein theradar receiver electronics are configured to convert the received radarreflections to an ultrasonic frequency range and to perform signalprocessing on the converted, received radar reflections in theultrasonic frequency range, wherein the ultrasonic frequency range is apassband that includes sixteen megahertz; and one or more processorsconfigured to generate a notification of target detection informationbased on the converted, received radar reflections, wherein the radartransmitter electronics are configured to output the monopulse radarsignals to a first coverage area, wherein the radar receiver electronicsare configured to receive the radar reflections from objects present inthe first coverage area, wherein the one or more processors areconfigured to generate the notification in response to a radarreflection received from the first coverage area, and wherein the firstcoverage area includes an area comprising a portion of the first wing.18. The aircraft of claim 17, further comprising a weather radar systemmounted in a nose radome of the aircraft, wherein the weather radarsystem is configured as a second obstacle detection system.
 19. Anvehicle comprising an obstacle detection system, wherein the obstacledetection system comprises: an integrated radar antenna, the integratedradar antenna comprising a multi-layer circuit board, the multi-layercircuit board comprising: a slotted waveguide radar transmit antenna; aslotted waveguide radar receive antenna; radar transmitter electronicsin signal communication with the slotted waveguide radar transmitantenna, wherein the radar transmitter electronics: are on a layer ofthe multi-layer circuit board different from the slotted waveguide radartransmit antenna and the slotted waveguide radar receive antenna, and inconjunction with the slotted waveguide radar transmit antenna, areconfigured to output monopulse radar signals comprising a fixedtransmitted radar pattern; radar receiver electronics in signalcommunication with the slotted waveguide radar receive antenna, whereinthe radar receiver electronics include digital beam forming circuitryconfigured to receive, from the radar receive antenna, radar reflectionscorresponding to the outputted monopulse radar signals wherein the radarreceiver electronics are configured to convert the received radarreflections to an ultrasonic frequency range and to perform signalprocessing on the converted, received radar reflections in theultrasonic frequency range, wherein the ultrasonic frequency range is apassband that includes sixteen megahertz; and one or more processorsconfigured to generate a notification of target detection informationbased on the converted, received radar reflections, wherein the radartransmitter electronics are configured to output the monopulse radarsignals to a first coverage area, wherein the radar receiver electronicsare configured to receive the radar reflections from objects present inthe first coverage area, wherein the one or more processors areconfigured to generate the notification in response to a radarreflection received from the first coverage area, and wherein the firstcoverage area comprises a portion of a perimeter of the vehicle.
 20. Thevehicle of claim 19, wherein the vehicle is an aircraft.